A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was, in Australia, known or that the information it contains was part of a common general knowledge as at the priority date of any of the claims.
Salt water chlorinators of the type with which the invention is concerned include an electrolysis cell to electrolyse chloride salts in the water to generate chlorine at an anode of the electrolysis cell. The chlorine reacts with a hydroxide (that is, sodium hydroxide NaOH) in the water (which, along with hydrogen gas is produced at the cathode) to form hypochlorite ions (from mainly sodium hypochlorite—NaOCl) as the primary sterilizing agent.
A problem with such electro-chlorinators is that scale (principally calcium salts) deposits and builds up on the cathode, thus reducing the efficiency of chlorine production by the cell. This problem has been addressed by periodically cleaning the cell, either manually by removing it from the chlorination system and soaking/scrubbing the electrodes in acid, or automatically by the system including means for injecting a dose of cleaning acid into the cell which remains in the cell for a predetermined time before being pumped out and into the body of salt water. Both the manual and automatic cleaning methods, apart from other problems, require consumers to handle acid which is generally not acceptable to consumers.
Another method for reducing the problem of scale build up has been to periodically reverse the polarity of the electrodes. However this requires more complex and thus more expensive control circuitry, and coatings have to be provided on all the electrodes. It also tends to shorten the lifespan of electrodes.
United States patents U.S. Pat. No. 3,432,420 (Pei-Tai Pan), U.S. Pat. No. 3,822,017 (W. Rast) and U.S. Pat. No. 4,668,369 (A. S. King) disclose use of mechanically driven scrapers within an electrolysis cell to remove deposits from a cathode. The applicant, however, is not aware of any such arrangements currently on the market and assumes that arrangements as exemplified by these US patents have not been effective, either operationally or for reasons of high manufacturing costs.
The present invention addresses the problem of scale build up on the cathode in a manner which reduces the disadvantages of the above described prior cleaning methods.